Method and apparatus for making artificial bristles



Dec. 23, 1941. H. A. NEVILLE 'ETAL METHOD AND APPARATUS FOR MAKINL: ARTIFICIAL BRISTLES Filed Sept. 13, 1959 'INVENTOR.

Cum 1/ WM ATTORNEY.

Patented ec. 23, 194i METHOD AND APPARATUS FGR G ARTIFICEAL BRITLES Application September 13, 1939, Serial N .-294,5'l2

(61. 9l-d6l 14 Claims.

Our invention relates to artificial bristles and more particularly to methods and apparatus for the production of tapered artificial bristles so that they have the general tapered form of natural bristles and are useful in brushes, especially paint brushes. I

This application is a continuation in part 05 our application Serial No. 243,318, filed Decembe: 1, 1938, and claims the method and apporatus for making the artificial bristles of that parent application.

In our copending application Serial No. 147,- 312, filed June 9, 1937, we have described certain forms of artificial bristles made from a composite oi textile fibers bonded together into trefoil form by a protective resinous coating, and have suggested tapering the bristles by repeated dippingin the coating solutions. Based upon extended research work and vtests along this line we have now discovered new and improved coating methods and means for making the tapered bristles either in one or multiple stage operations. We have icund that our new development is applicable to a variety of base materials and may be applied to separate lengths of filaments or may be used to produce a continuous coated filament of varying cross-section.

In accordance with our present invention we have found that tapered artificial bristles' having superior properties may be produced by immersing a filament in a relatively viscous coating solution and withdrawing the filament from the solution at a changing rate of withdrawal, increasing or decreasing. The filament, as withdrawn, has a coating of variable thickness of the coating material. The more rapid the rate of withdrawal of the filament the greater the amount of viscous solution retained on the filament and accordingly the thicker the layer of adhering coating. Decreasing the rate of withdrawal produces the'opposite efiect, namely, a

decrease in the thickness of the coating; Because of these phenomena we are able to produceupon a filament a coating. or uniformly decreasing thickness, which is in eflect a taper,

by graduallyincreasing the rate of withdrawal found that it is desire-hie to have presentcertain conditions, as follower The coating solution which is to be applied to the filaments for increasing its resistance to water, solvents, allralis, acids, etc, and which in some instances may also be used for tapering the filament, must be substantially prevented from flowing alone the filament core after the coated filament is withdrawn from the solution. Otherwise, the material would build-up in places end he too thin in other places causing nonuniiormity of coating thickness as well as nonuniformity of taper "The same is true where a separate solution is used for tapering. We have found that any substential amount or flowing may be prevented by one or a combination of the following methods:

A. Using a very volatile solvent, e. g. acetone. in the coating material solution so that asscon as the coated filament is withdrawn from this solution the solvent will evaporate rapidly and cause gelation or other solidification or the coating material about the. core filament. This rapid solidification of the coating upon exposure to the atmosphere will cause it to retain its desired position on the filament. The rate of evaporation may be accelerated by partial evacnation-of the space surrounding the coated filement or by providing a current of air to carry of the filament from the coating solution in -which it is immersed. The form of the coated filament is like that of an animal, (e. 'g-. hog) bristle, in that it has a butt end or relatively large diameter and a tip end of relatively small diameter, with proportionately varying diameters in between the butt and tip ends.

To produce the desired type-o! taper on the away the vapors.

B. Rapidly decreasing the temperatureof the fluid coating material on the filament immediately after it leaves the reservoir of coating solution, so that the material gels or solidifies before it has an opportimity to flow on the filament. Suitable refrigerating means such as a current or cold air or an artificially refrigerated enclosure for the coated filament might be used to hasten the solidifying or gelling or the coating.

C. Rapid solidification of the fluid coatin material on the filament may also be obtained by using the coating material in the form or a thlxotropic dispersion that will set to a gel very quickly upon application to the filament.

Unless one or more or these several methods of producing rapid gelation ortheir equivalent is utilized. the fiuid coating will tend to fiow along the filament or will be drawn into droplets or beads on the filament by the forces of coated filament as above desc i W as i I! the entire filament to becoated-iswound brush bristles.

upon a frame and is immersed in the coating solution and withdrawzuwhether it be of a length adequate for making one bristle or several, the

withdrawal of the-frame and filament from the solution would be at a predetermined rate of acceleration or deceleration to efi'ect the desired taper. Such'an operation would be used where it is desired to produce in batches one or several bristles at a time, and then repeating the opup. of one or more of suitable, core materials such as those described above.

The coating materials used for coating or tapering the filament cores may be selected from a large class of different substances and are normally used in the form of solutions or dispersions. These materials include thermoplastics such for example, as cellulose acetate or other cellulose derivatives; oleo resin varnishes; alkyd varnishes, urea-formaldehyde varnishes; phenolformaldehyde resin; vinyl resins such aspolymerized vinyl chloride and vinyl acetate or 00 v polymerized mixtures thereof; vinyl acetates and continuously coated filament having thick and thin sections at regular intervals will be produced. The rate of taper and the length of the tapered portions of the filament may be controlled by the withdrawal cycle such that the continuously coated filament having alternately thick and thin portions may be cut at points of maximum and minimum thickness to produce individual bristles, the length and degree of taper of each such bristle being determined, as mentioned above, by the nature of the withdrawal. cycle.

The filament core materials that may be used in our invention vary widely in their characteristics and may be selected from one or more of the following classes of materials: textile fibers, such as natural silk; or certain artificial silks, such as that disclosed in Carothers Patent No. 2,130,948,issued September 20, 1938, or certain vinyl polymers extruded into fibers, cotton, regenerated cellulose,-cellulose acetate, other cellulose esters and ethers, glass; metals such as steel, copper, copper alloys, aluminum, aluminum alloys and silver, the non-ferrous metals being preferred ,because of their resistance to rust; and any other similar suitable materials that can be spun or drawn into continuous filaments which have the flexibility and strength required for The choice of these materials depends somewhat upon the,use to which the final bristle is to be put and is dictated by such factors as tensile strength, resistance to solvents, flexibility and stiffness of the materials. The core filaments may be individual filaments or may consist of a strand or thread made up of a number of filaments. We have found that threads composed of a plurality of continuous filaments substantially parallel or with a slight twist are desirable and offer advantages over threads made of spun fibers. Different sizes of yarns may be used so that a better filling of the voids is obtained on blending the resulting bristles. As anexample, a coarse product is ob-' tained by winding frames with one strand,

(composed of. many individual filaments), of 150 denier cellulose acetate yarn. An intermediate product is obtained from frames wound with one strand of 100 denier cellulose acetate yarn and a fine product from frames wound with one strand of 45 denier cellulose acetate yarn. These yarns may be wound in multiple. For example,

if three strands of 45 denier are wound as a unit, V. a product comparable to that from one strand of 150 denier yarn is obtained. However. thereis some improvement in stiffness, due to the trefoil structure.

The word "'fllamen as used in the specification and claims herein is used in a generic sense .and is intended to include the various forms of fibers, filaments, strands, threads, etc. 'made their selection'will depend somewhat upon the procedure adopted for gelling or solidifying the coating material on the filament promptly upon withdrawal of the filament from the coating mixture. Where the gelation or solidification is dependent solely or primarily upon the volatility of the solvent such rapid vaporizing solvents as acetone, methyl acetate, ethyl acetate, methyl formate and benzene and the like, and certain of the chlorinated solvents such as chloroform and dichlorethylene may be used. Where one of the other means above described is used for accelerating the gelation or solidification of the coating on the filament slower drying solvents such as for example certain of the refined petroleum and coal tar distillates, e. g. xylene. varsol and high-flash naphtha may be used.

In accordance with our invention the artificial bristles may be made by applying one or several coatings to'the filament core material. For example, where the filament core material consists of metal, only one type of coating will be required for giving the bristle, the desired resistance to water, acid, alkalis, etc., and also for effecting the desired taper of the bristle. In such a case the coating material may advantageously be selected from the above mentioned classes of resins or varnishes which would give the filament the desired resistance to attack by liquids and the necessary tensile strength where required. This varnish or resin coating may be applied in one application, that is, one immersion of the core material in the coating solution and withdrawal therefrom, or several of giving the filament the desired resistance andstrength and the other coatings the desired taper required to simulate natural bristles.

The method of and apparatus for making the tapered coated filaments of our invention may be more clearly understood from the followingdetailed description taken in conjunction with the accompanying drawing in which illustrating thecoated filament being withdrawn from the coating container;

Fig. 3 is a longitudinal sectional view of a aaoaaor piece of filament coated by the system shown in a is a diagrammatic representation oi a system for continuous coating and tapering oi the filament; and

Fig. is a longitudinal sectional view of a portion or a tapered coated bristle having a metal core and one layer of coating.

Referring now to the several figures inthe drawing, generally in the order in which they occur, there is shown in Fig. l a frame it with the filament Ii wound thereon, the filament in this specific but non-limiting embodiment of the invention being a cellulose acetate fiber. The filament is wound on the frame i!) by clamping the frame in a mechanical winder (not shown) with a traveling guide so that as the frame is rotated the guide moves from one end of the frame to the other and thereby produces a spiral wind of the filament on the frame. An example of the pitch of this winding is ten turns to the inch. The ends of the filament may be fastened to the frame in any suitable manner such as by tying to a cross member of the frame.

The textile fiber filament, i. e., cellulose acetate in this example, being wound on the frame, the next step is to dip the wound frame in a bath containing a suitable varnish or resin solution to coat the textile filaments. A system suitable for that purpose is shown in Fig. 2. As shown in that figure a dipping tank i3 is approximately filled, for example, within one-half of an inch of the top'of the tank, with a resin solution indicated at M. In this specific arrangement the dipping tank is of sufficient capacity to accommodate only one frame, (a laboratory size being 13 inches long, 7 /2 inches high, and /2 inch wide), but it is to be understood that in commercial production larger tanks would be used, such, as to accommodate two or more rows of frames. In such an arrangement the filaments may be dipped and coated and after coating. may be cut at the top and bottom to form the individual bristles; and the plurality of frames may be held in parallel and dipped together in one operation. To facilitate handling of the filaments after coating the uppermost portion of the filaments, e. g. /2 inch. is not immersed in the coating material and this uncoated portion is cut off when the filament is cut into individual bristles. I

The meansv for withdrawing the frame and coated filament from the dipping tank l3 comprise two cords l5 having hooks l6 for engaging the eye extensions I2 on the frame 10. The cords i5 extend and are movable over pulleys I1 rotatably mounted on an axle IS. The cords I5 also extend over a second pair of pulleys l9 rotatably mounted on an axle 20. The cords are joined at the ends remote from the dipping tank, to a member 2| by means of the hook and eye' arrangement shown generally at 22. The member 2|, which is in the form of a flat, narrow board or metal strip is attached to or is integral with a plunger 23-which is adapted to work in an oil cylinder 24. The cylindrical container 25,

' from the coating composition ll shown in Fig. 2

which is attachedto the top of the plunger 23,

and the inlet pipe 26 with valve 2'l-are not used in this preliminary coating process but are used in the tapering treatment described below.

The coating solution l4 in the dippingtank l3 may be selected as above noted from a large member of resin solutions, examples being straight and dryingoil modified phenol formaldehyde resins; drying oil modified alkyd resins;

vinyl resins, e. g. vinyl chloride vinyl acetate resin; cashew nut shell oil varnish; and straight or plasticiaecl urea iormaldehyde. We have duced very satisfactory results with. a fihinawood oil modified phenol formaldehyde enamel which is made up according to the following formulae under Example I:

Emmott: l

Varnish composition Fer cent China-wood oil L25 Phenol-formaldehyde resin, e. g. Kit-223i Bakelite 25 Hi-fiash naphtha 25 Solvent naphtha 25 Viscosity (3-H (Gardner-Holt tubes) Enamel composition Another example of a coating composition that we have found to give entirely satisfactory resuits is as follows:

Exmeu: II Pounds Uformite F-225 (a'urea-formaldehyde resin' dissolved to solids in 'xylol and butanol) 55 Castor oil modified alkyd resin (50% solids and 50% oil modified) 35 Xylol g- 10 In the specific case being described, we use for the coating material, the enamel composition shown above under Example I. The frame H) with filament Ii wound thereon is immersed in the coating solution ll for a short time, for 'example 1-2 minutes.

The withdrawal of the filament and frame is carried out by raising the plunger 23 to its full height and connecting the cords l5 with the frame ID by meansof the hooks IS. The plunger 23 is then permitted to travel downward in the oil cylinder 24. In this example the time-of withdrawal was about 1 minute and 15 seconds. and the frame is withdrawn at a constant or steady rate of withdrawal as the plunger slowly drops through the 011. To facilitate drying of the coating on the filament during the withdrawal operation, additional means such as electric fans 28, as shown in Fig. 2, may be used. These fans will blow a current of air against the coated, filament as it emerges from the coating tank and it is desirable tohave these fans blow the air upward at an angle of,- about 45" along the front and back edge of the top of the tank l3. These two streams of air meet at the frame and follow it upward during the withdrawal.

The coated filament still wound on the frame and after air drying to permit the major portion of the solvent to evaporate, is baked in an oven at about C. for a period of about 45 min utes to 1' hour. The resinous enamel coating content used was about 15% to 30%.

-onds to 15 seconds on this arbitrary scale.

thus produced on the filament serves .as a protection of the textile fibers of this filament, e. g., cellulose acetate, from the solvent action of the tapering solution which is next to be applied as follows:

The coated filament still wound on the frame is allowed to cool after the above baking treatment and is then again dipped in the tank 13,

from which the resin solution has beenremoved v solution is cellulose aceto-butyrate in acetone solution.

We have found that it is important to have good control of the viscosity of the tapering solution, and we have determined the permissible viscosities by testing such solutions in a tube having two marks eight inches apart. The test is made by noting the time required for a steel ball (in this case having a diameter of inch) to fall between the two marks in the cellulose acetate solution and we have obtained satisfactory results with solutions tested in this manner having variations in viscosity from about 6 sec- We prefer a range of approximately 8 to 12 seconds; a second solution being a good average. If

the viscosity is too great or the speed of withdrawals of the filament too fast as above explained, the solution fills in and forms a web between adjacent threads. Also if the viscosity is too low there is a tendency to produce'a wavy coating which has in effect a modified droplet formation.

In carrying out the tapering process we have found it necessary to have the tapering solution, e. g. cellulose acetate, come as near the top of the container l3 as possible. In this connection we have obtained satisfactory results by filling the container to about A inch from the top with the tapering solution. If the solution is not near enough to the top the coating material starts to flow down along the filament when the latter is withdrawn and a poor taper results. This is apparently caused by the atmosphere just above and thereby increase the speed of withdrawal of ing described above.

the solution in the container being saturated with the solvent vapor, which prevents rapid evaporation of the solvent contained in the coating material on the filament core. The frame with coated filament wound thereon as described above, is immersed in the tapering solution now contained in the tank l3 and then promptly withdrawn from this tapering so- 1 lution at a steadily increasing rate. Thiswithdrawal is accomplished by the same procedure a stream of mercury or other suitable liquid is fed through the pipe 26, controlled by valve 21, into cylindrical container 25. Instead oi. a liquid, a suitable solid, which will pour, suchas for example sand, may be supplied tothe container 2i. nThe accumulating increase in weight on the described above for the first coating except that speed may beso adjusted as to efiect the withdrawal of the frame from the tapering solution in a period of about 30 to 35 seconds depending upon the size of the frame. By steadily increasing the rate of withdrawal, no droplets of excess material are formed. on the filament and the desired taper is produced by'the varying amount of cellulose acetate material retained over the length of the filament. The current of air from the electric fans 28 or other suitable means may also be used in this instance to facilitate drying of the tapering solution if desired.

After the frames, with tapered coating on the filament, are air dried to remove the major portion of the acetone solvent, requiring about 1 hour at room temperature, the frames are given another dipping in the resin solution, the same or similar to that used for producing the first coat- It will be understood for this operation that the tapering solution is removed from the container i3 and substituted by a resin solution such as described above under Example I for effecting the final protective coat on the tapered filament. To avoid filling and refilling of' the tank l3 with the above solutions separate dipping tanks may be employed for the coating and tapering compositions.

After the tapered and coated filament is withdrawn from the final coating solution it is again baked for a period of about 2 hours at about ,C. This baking treatment will vary of course with difierent types of coating and'tapering solutions. The above example of temperature and time is based upon use of the black phenol formaldehyde enamel described under Example I, and

the use of cellulose acetate plasticized with the plasticizer known as Santicizer M-l'l for the tapering solution. If the cellulose acetate is not plasticized and a urea formaldehyde resin is used, the baking time would be about 45 minutes at about C.

When the final baking operation above described has been". completed the individual strands are cut from the frames at top and bottom, the cutting at the top being from about V;

of an inch to 1% of an inch above the limit of the cellulose acetate coating, that is the tapering solution. For making one type of brush bristle the bundle of tapered filaments is cut to a length of about 5 inches and is now ready to beblended with others of the same and different sizes to make up the paint brush formula.

Measurements of the tip and butt ends of the coated and tapered filaments described above are given below to show the extentof taper over a length of about 5% inches:

Tip diameter-- Butt diameter bristle as defined in claim 1 in which the tapered coating comprises a resinous material.

6. A method of making an artificial tapered bristle as defined in claim 1 in which the tapered coating comprises a thermoplastic resin.

7. A method of making'an artificial tapered bristle as defined in claim 1 in which the tapered mating comprises a vinyl resin.

8. A method of making an artificial tapered bristle as defined in claim 1 in which the tapered coating comprises a vinyl formal.

' 9. A method of making an artificial tapered bristle as defined in claim 1 in which the tapered coating comprises a vinyl acetai.

10. A method of making artificial bristles as defined in claim 1 in which the filament is a textile filament.

11. An apparatus for producing tapered coatings on artificial bristles comprising a frame for supporting the bristle core filament, a container for the filament coating solutionand means for withdrawing said frame and filament from. the coating solution comprising a plunger connected to said frame, an oil cylinder, in and out of which said plunger is-adapted to move, a container mounted onsaid plunger and a supply of materialv adapted to fiowinto said container and progressively increase the weight on said plunger whereby the rate of withdrawal of said filament by said plunger is varied.

12. An apparatus for making an artificial tapered bristle comprising means for immersing a filament in a coating solution to produce a coating on said filament and means for withdrawing said filament from said coating solution at a varying rate of withdrawal, including means whereby the change in rate'of withdrawal is mechanically controlled, to cause a varying amount of coating material to be retained over the length of the filament and thereby produce a tapered coating on said filament.

13. An apparatus for making an artificial tapered bristle as defined in claim 12, in which the filament withdrawing means comprises an oil cylinder and a plunger adapted to move in and out of said cylinder.

14. An apparatus for making an artificial tapered bristle as defined in claim 12 in which the means for varying the rate or withdrawal of the filament comprises an oil cylinder and a plunger adapted to move in and out of said cylinder and a supply of mercury adapted to vary the weight of said plunger and progressively increase the speed of its movement into said oil cylinder.

HARVEY A. NEVILLE. WILLIAM c. FORBES. 

